Apparatus for forming hollow bodies

ABSTRACT

A machine for blow molding hollow bodies such as bottles from extruded tubular plastic material includes a plurality of molds which are guided over a closed path including a straight portion coaxial with the extruder by means of a first follower constrained to follow a closed loop path and second and third followers engaging with guide surfaces which extend over fractions of a closed loop path.

PATENIEmusza ma 3.685; 93a

SHEET 1 F 3 INVENTOR.

Serge Logourte United States Patent Lagoutte [451 Aug. 22, 1,972

[54] APPARATUS FOR FORMING l-IOLLOl 2,579,399 l2/l951 Ruekbeirg ..18/5BP BODIES 3,334,379 8/1967 Settembrini ..18/5 BP Inventor: rge Lagoutte,Chalon sur saone Bronn .t l France j 3,546,747 12/ 1970 Stefaniak et al..18/20 B [73] Asslgnee: 830:2; dnltde/SA ,yengrll gli: PrimaryExaminer-J. Spencer Overholser gege (Hautslds'ei'n) France)l AssistantExaminer-Michael O. Sutton t Attorney-Pennie, Edmonds, Morton, Taylorand [22] Filed: Aug. 7, 1970 Adams 21 A l. No.: 61 998 l pp [57]ABSTRACT [30] Foreign Application Priority Data A machine for blowmolding hollow bodies such as bottles from extruded tubular plasticmaterial includes Aug. 12, 1969 France ..6927662 a plurality of moldswhich are guided over a closed [52] U.s. ci. ..425/185, 425/233 425/305Path including a Straight Portion Coaxial with the ex- 425/326 truder bymeans of a first follower constrained to fol- [51] im. cl. 329e 3/00,B29d 23/03 10W a Closed loop path and Second and third followers [58]Field of Search ..18/5 BP, 5 BE, 20 B; 74/63 engaging with guidesurfaces which extend over frac tions of a closed loop path. [56]References Cited 4ck-w 4 Figursw H UNITED STATES PATENTS 3,310,8343/1967 Simpson et al ..18/5 BP PTEN'TEmuszz ma y 3,585,938

' SHEET 2 HF 3 INVENTOR.

Serge LogouHe ATTORNEYS PATENTEDmsea |912 3.685.938 snm 3 uf INVENToR.

Serge LogQurTe @fn/MIM M 'ATTORNEYS APPARATUS FOR FORMING HOLLOW BODIESIt has been heretofore proposed to make hollow objects of plasticmaterial by blowing them in molds from short lengths of tubular plasticmaterial continuously extruded from a die.

In machines employed for this purpose there is generally provided a moldcarrier, which may have a rotary motion for example. This cam'ersupports a number of molds each made up of two mold halves. By themotion of the carrier the molds move successively through a closed path,at one point of which the opened halves of each mold close upon a lengthof plastic tubing extending from an extruder The tubing within the moldis thereupon blown to conform to the desired shape. The carrier thenmoves the mold on to a subsequent location in the closed path where themold halves are opened for ejection of the molded piece.

In order to obtain satisfactory operation of a machine of this type itis necessary that before the molds close, the halves thereof be broughtto a position which is aligned with the extrusion axis. It is moreovernecessary that, after the mold halves have closed, they shall move alonga rectilinear path which is coaxial with the extruder axis until thenext following mold shall have closed upon the next following section oftubing. It is also necessary that when this next mold closes it be asclose as possible to the previous mold in order to minimize the lengthof plastic tubing which is lost between the two molds and whichconstitutes waste material.

These two requirements thus imply:

a. articulated mounting of the molds on the carrier therefor, where theyundergo a generally rotational motion with constant angular speed, so asto make possible a temporary coaxial positioning of the molds with eachother, at least in pairs;

b. guidance of the molds so as to impose upon them during this phaserectilinear motion along a path coaxial with the extruder; and

c. compensation of the variations in the radius of gyration of the moldsabout the principal axis of rotation of the mold carrier during therectilinear phase of mold motion.

Articulation of the molds does not present any particular problem and isgenerally realized by mounting the halves of each mold for slidingmotion (for purposes of opening and closing the mold) on a cradle whichin turn is articulated at each end to the mold carrier along an axiswhich may be parallel both to the axis of rotation of the carrier and tothe direction of motion of the mold halves with respect to each other.

The guidance of the molds required to impose on them the desiredrectilinear motion parallel to the extrusion axis can be effected bymeans of cam followers mounted on the mold-carrying cradles andcooperating with cams or guide surfaces fixed in the machine frame.

As to the compensation for variations in the radius of gyration of themolds during the rectilinear phase of their motion, this can be achievedby various means such as slides, slots, telescopic arms, springs,articulated arms and the like, interposed between the mold carrier andthe cradles.

Machines of the several known types which operate on the principlehereinabove described include in general a large number of molds, someor more, mounted substantially in contact with each other so as to coveror occupy substantially the entirety of their own closed trajectorywhile preserving between adjacent molds as small a spacing as possiblesince it is this spacing which determines the length of waste plasticbetween successive molded articles.

There is thus automatically satisfied the desired condition of proximityhereinabove mentioned, namely the condition that between a given mold atthe time of its closure and the mold which has preceded it, the spacingbe as small as possible. On the other hand, in the known machines abovereferred to it is not possible arbitrarily to change the number or thedimensions of the molds without also changing their mutual spacing andthereby the amount of material lost.

Moreover machines of these known types accommodate only a relativelylarge number of molds, which is satisfactory for long production runsonly.

Applicants copending application Ser. No. 774,386, filed Nov. 8, 1968,and assigned to the assignee hereof, discloses a machine which can beemployed for short production runs and which can be built for a numberof molds as small as three. In the machine of that application, motionof the molds (over part of their path) coaxially or collinearly withrespect to the extrusion head requires a movable mounting of themold-carrying cradles on the mold carrier. In addition the desiredproximity between each mold at the time it closes and the preceding moldmakes it necessary to change the intermold spacing over the closed pathof mold travel, since the length of this closed path is necessarily muchgreater than the aggregate length of the molds themselves takenend-to-end.

'I'hus the machine of that application spaces the molds in the desiredproximity to each other only in pairs and only at the time when a moldcloses on the plastic tube delivered by the extruder, this mold thenbeing in the desired condition of proximity to the mold which haspreceded it. Thereby the machine of that application achieves a minimumwaste of material, even with as few as three molds and despite the factthat the molds are more widely spaced one from the other on theremainder of their cyclic closed path of travel.

In one embodiment of the machine of that application the variation inthe radius of gyration of the molds about the axis of the mold carrieris obtained by mounting the cradles on the carrier by means of hinged orarticulated arms, i.e., at the ends of rods, which are hingedly coupledto cranks constituting spokes of the carner.

Such a machine, while operating very satisfactorily notwithstanding thesmall number of molds involved, does not permit wide latitude inchanging in the dirnensions of the molds.

lt is consequently an object of the present invention to provide amachine having the advantages of the machine of application Ser. No.774,385, namely minimum loss of raw material between successive moldsand a small number of molds such as three, and having the additionaladvantage that the length or other dimensions of the molds which can beemployed in a given machine may be varied over wide limits.

It is another object of the invention to provide such a machine of smalldimensions and hence with a small radius of rotation for the molds. ltis still another object of the invention to provide a machine in whichthe guiding of the molds is effected ina highly dependable way and withreduced stress on the elements involved.

Hereafter the element which supports the molds will be described asthetumtable.

By reference to the machines of the prior Aart hereinabove mentioned,the machine of the present invention is characterized by the fact thatthe mold-carrying cradles are articulated at each end on a rod which inturn is pivotally connected to a crank or spoke fixed on the shaft ofthe turntable, and by the fact that guiding of the cradles lengthwise ofthe rectilinear portion of their motion and their correct orientationduring that portion of their motion are assured by three camsandfollowers. The first of these followers is constrained by a closedgroove constituting a face cam, and cooperates successively with theother two followers whose cams or guide surfaces take the form of opengrooves, each engaging vits follower over only a part of the closedcycle of motion of that follower.

In a preferred embodiment the machine according to the invention ischaracterized additionally by the fact that the point of articulation ofeach rod to its crank is adjustable between the limits lengthwise ofthecrank.

'I'he invention will now be further described in terms of a preferredexemplary embodiment thereof and with reference to the accompanyingdrawings, in which:

FIGS. I and 2 are diagrams useful in explaining the invention;

FIG. 3 is a sectional view in elevation of the machine, the extruderbeing however omitted', and

FIG. 4 is a sectional view illustrating the construction of the camfollowers.

In FIGS. 1 and 2, wherein the mounting and guiding of the cradles on theturntable is schematically inthe arm 1' of cradle l carry auxiliaryfollowers 8 and 9.

dicated, O is the axis of rotation of the turntable 14 and so that theelective length of the crank arms is adjustable. The cradles l, la, and1b are in turn hingedly, i.e.,

pivotally, connected to the connecting rods 3, 3a, and 3b at the outerends of the latter, the hinge points being denoted 5, 5a, and 5b. In theschematic representation of FIGS. 1 and 2, the cradles are shown asincluding,- as rigid elements thereof, arms l', la', and lb' for thispurpose.

In the operation of the machine, the turntable 14 to which the crankarms 2, 2a, and 2b are fixed is caused to rotate in the sense of thearrow F. Thus the hinge points 4,'4a, Vand 4b between the connectingrods 3, 3a, and 3b and their respective crank arms 2, 2a, and 2bdescribe a circle of adjustable radius R having its center at O.. Duringthis motion the connecting rods 3, 3a, and 3b carry with them the axes5, 5a, and 5b of articulation of the mold cradles to the connectingrods. These hinge axes are constrained by first followers 7, 7a, and 7bto move in a closed lpath 6 defined by a stationary face cam, indicatedat 30 in FIG. 3. The followers 7, 7a, and

In similar fashion, arms 15d and 16a fixed with respect to each otherand to arm la' of cradle la carry auxiliary followers 8a and 9a, andarms 15b and 16b fixed with respect to each other and to arm 1b ofcradle lb carry auxiliary followers 8b arid 9b. For simplicity thefollowers 7, 7a, and 7b have been shown in FIG. 1 as coaxial withv theaxes 5, Sa, and 5b. While this is ari advantageous form of construction,it is not essential to the invention. k

With the hinge axes 5, 5a, and 5b carried and guided lengthwise of theclosed path 6 by the followers 7, 7a, and 7b, there remain to beprovided means to orient the cradles correctly along their trajectoriesand in particular to keep the molds coaxial with the extrusion axis xx'while the followers 7, 7a, and 7b execute the rectilinear portion oftheir motion along the path 6. This result is obtained by cooperation ofthe r'nain followers 7, 7a,

and 7b with the auxiliary followers 8 and 9, 8a and 9a plane of thefigure. In this figure it will also be seen that.

the cradle la is being guided by its main follower 7a still in thestraight portion of the path 6and by its follower 9a after entry of thelatter into a path 10, defined by a ca m or groove 31, whereas thefollower 8a has emerged from the path l1, which terrriinates at ll. Inthe position shown in FIG. 1, it can be seen that the two molds 1 and 1aare coaxial, the axes of the molds being in alignment with the extrusionaxis xx'.

A slightly later phase in-the rotation of the turntable 14 isillustrated in FIG. 2. There the cradle l continues to be guided alongthe rectilinear portion of its path, collinearly with the axis xx', byfollowers 7 and 8in the straight portion of paths 6 and 11. Cradle lahas however departed from collinearity with axis xx'; its main follower5a has entered the curved portion 6a of cam groove 6.

'Ihe path l0 of the followers 9, 9a, and 9b defined by cam 3l extendsfrom 10a to l2, counterclockwise as seen in FIG. 2, whereas the path offollowers 8, 8a, and 8b extends counterclockwise from 13 to 11'. The camdefining this path is, as previously stated, beneath the plane of thefigure. The path 6 ofthe followers 7, 7a, and 7b on the other handextends over 360 about the axis O, although it is not circular. Beforethe followers 9, 9a, and 9b reach the end 12 of their path l0, thefollowers 8, 8a, and 8b reenter their path at the point 13.

This ensures again correct guidance of the mold cral substantially theposition shown for cradle I in FIG. v2,

where its guidance will be assumed by followers 7b and 9b it will beobserved um me length of the radius R of the turntable (i.e., of thearms 2, 2a, and 2b) is of substantially the same order as the lengths ofthe arms .15 and 16. Under these conditions the use of the two auxiliaryfollowers for guidance of the main follower and their alternatecooperation with the central one, but over separate fractions of the 360angle about the center O, makes it possible to reduce substantially thesize of the machine and in particular the length of the straight centralportion of the path 6 for the main follower without changing therectilinear portion of the path followed between molds. This reductionis substantially equal to the distance between the followers 7 and 8,which means a reduction of some 30 percent in the straight portion ofthe path 6. This is highly advantageous and makes it possible to mounton such a machine molds whose length is for example of the same order asthe maximum radius of the turntable or indeed greater than that radius,as had not heretofore been possible, in particular in machinesaccommodating a large number of molds.

In other words, the machine according to the invention is much morecompact. It is moreover lighter. Moreover, a calculation shows that byvariation of the radius R it is possible, without changing their camsand their followers, to vary within wide limits the length of the moldswhich can be mounted on the machine.

ln a machine according to the invention which has been satisfactorilyoperated, the ratio of the maximum mold length (approximately 360 mm.)to the minimum mold length has been 1.4, the maximum and minimum valuesof R being respectively 225 and 146 mm.

The distance separating the auxiliary followers from their associatedmain followers being in practice approximately equal to the minimumvalue of the radius R, it will be apparent that the guidance which thesefollowers produce is very stable.

FIG. 3 represents the machine schematically shown in FIGS. 1 and 2,reversed however left for right. In FIG. 3 the mold-carrying cradles areshown at l, la, and 1b substantially in the positions shown for them inFIG. 2.

The turntable 14 is driven by a shaft 20 from a motor via a suitablereduction gear. The crank arms 2, 2a, and 2b are fixed to this shaft andthe connecting rods 3, 3a, and 3b are articulated to these crank arms.The effective length of the crank arms is adjustable by means of slidingjoints 21 whose position is adjustable by means of screws 22 engagingelements 23 fixed to the outer end of the crank arms.

lt can be seen in FIG. 3 that the axes 5, 5a, and 5b of articulationbetween the rods 3, 3a, and 3b and the cradles coincide with those ofthe followers 7, 7a, and 7b. The cradles include as rigid elementsthereof arms 24 joumaled about the axes 5, 5a, and 5b and fixed to thearms and 16 carrying the auxiliary followers.

The machine is supported on a base 26 which rests upon a carriage 27.

FIG. 4 shows the arms l5 and 16 which support the auxiliary followers 8and 9. lt will be observed that the followers 7 and 9 are at the samelocation lengthwise of their own axes, while follower 8 is axiallydisplaced therefrom.

Auxiliary elements have been omitted from the drawings such as thosewhich open and close the molds, these being optionally of known type.

It is also possible, in accordance with the invention, to use one ormore turntables interchangeably mounted on the carriage and to changethe molds of one tumtable during operation of the machine with anotherturntable. The extruder and driving motor may be fixed as a unit withthe shaft of the turntable coupled to the motor shaft when the turntableis in operating position.

With the dependable guidance provided by the wide separation of thefollowers, it is not necessary to provide guidance for the cradles attheir two ends and it is sufficient to provide for each cradle threefollowers situated on the same side of the cradle by reference to acentral symmetry plane ofthe machine.

The invention thus provides apparatus for blow molding hollow articlesfrom tubular plastic material extruded along an axis, said apparatuscomprising a plurality of molds, a first cam 30 having a closed profile,two cams 3l and 11 having open profiles, three cam followers such as 7,8, and 9 coupled to each of said molds, each of said followers engaginga separate one of those cams, and drive means to drive the molds in aclosed path under guidance of their respective followers. The drivemeans may comprise a shaft 20 and a separate linkage coupling the shaftto each of the fol lowers such as follower 7 engaging the closed profilecam. The linkage may include for each mold an arm such as the arm 2 xedto the shaft 20 and a rod such as the rod 3 connecting the arm to thefollower such as 7 engaging the closed profiley cam. Means may beprovided, as shown at 2l and 22 in FIG. 3, to adjust the point ofcoupling 4 of the rod 3 lengthwise of the arm 2, and similarly of coursefor the other molds. The cam 30 having a closed profile includes aportion parallel to the axis of the extruder, and so does at least oneof the open profile cams 3l and 11. For each mold, the spacing of thefollower engaging the closed profile cam 30 from the associatedfollowers, such as followers 8 and 9 for the mold l, which engage theopen profile cams 31 and 11, may be of the same order of magnitude asthe length ofthe arm affixed to the shaft.

The means for pinching the ends of the tube section trapped in each moldwhich means may be pan of the mold itself) and the means for deliveringair or other gas under pressure to the interior of such tube sections inorder to blow mold them may be conventional in nature and have not beenshown in the drawings.

While the invention has been hereinabove described in terms of apresently preferred embodiments, the invention itself is not limitedthereto but rather comprehends all modifications of and departures fromthat embodiment properly falling within the scope of the appendedclaims.

I claim:

l. Apparatus for blow molding hollow articles from tubular plasticmaterial extruded along an axis, said apparatus comprising a pluralityof molds, a first cam having a closed profile, two cams having openprofiles, three cam followers coupled to each of said molds, each ofsaid followers being engageable with a separate one of said cams, adrive shaft, and, for each of said molds, an arm xed to said shaft and arod pivotally connecting said arm to the follower engaging said closedprofile cam.

2. Apparatus according to claim 1 including means to adjust the point ofcoupling of said rod lengthwise of said arm.

. 3. Apparatus according to claim 1 `wherein the spacing of saidfollower engaging said closed profile cam from said followers engagingsaid open profile cams is of the same order of magnitude as the lengthof said arm.

4. Apparatus for blow molding hollow articles from tubular materialextruded along an axis, said apparatus comprising a stationary face4 camhaving a lclosed profile including a straight portion parallel to saidaxis, a plurality of stationary face cams having open profiles eachincluding a straight portion parallel to said firstfirst followersthrough the closed path defined by said cam having a closed profile.

1. Apparatus for blow molding hollow articles from tubular plasticmaterial extruded along an axis, said apparatus comprising a pluralityof molds, a first cam having a closed profile, two cams having openprofiles, three cam followers coupled to each of said molds, each ofsaid followers being engageable with a separate one of said cams, adrive shaft, and, for each of said molds, an arm fixed to said shaft anda rod pivotally connecting said arm to the follower engaging said closedprofile cam.
 2. Apparatus according to claim 1 including means to adjustthe point of coupling of said rod lengthwise of said arm.
 3. Apparatusaccording to claim 1 wherein the spacing of said follower engaging saidclosed profile cam from said followers engaging said open profile camsis of the same order of magnitude as the length of said arm. 4.Apparatus for blow molding hollow articles from tubular materialextruded along an axis, said apparatus comprising a stationary face camhaving a closed profile including a straight portion parallel to saidaxis, a plurality of stationary face cams having open profiles eachincluding a straight portion parallel to said first-named straightportion, and a plurality of mold cradles, said machine furthercomprising for each of said cradles a first follower engaging saidclosed profile cam, auxiliary followers engageable each with a separateone of said open profile cams, and means supporting said cradle andsupporting said followers for rotation about axes fixed with respect toeach other and to said cradle, said machine further comprising means todrive said first followers through the closed path defined by said camhaving a closed profile.